It's a Bootstrap plugin to help you center columns and galleries.
New in 3.3.0 : you can now enable or disable the features you don't need so that lighten the final compiled code!
Only available with the Less version of bootstrap and so only for Bootstrap 3.x. The SASS version for Bootstrap 4.x will come as soon as possible.
Auto calculation of the offset needed to center a group of columns with of size of x columns.
Auto calculation of the offset needed to center the last elements of a gallery. Limited to the maximum possible size of a column for a gallery.
Same operation as for versions center but the columns are centered equidistantly from each others.
Check the demonstration on codepen
<div class="center-column-xs-9 center-column-sm-9 center-column-md-9 center-column-lg-9">
<div class="col-xs-2 col-sm-2 col-md-2 col-lg-2">
<p>.col-lg-2</p>
</div>
<div class="col-xs-5 col-sm-5 col-md-5 col-lg-5">
<p>.col-lg-5</p>
</div>
<div class="col-xs-2 col-sm-2 col-md-2 col-lg-2">
<p>.col-lg-2</p>
</div>
</div>
<div class="center-column-xs-9 center-column-sm-9 center-column-md-9 center-column-lg-9">
<div class="col-xs-3 col-sm-3 col-md-3 col-lg-3">
<p>.col-lg-3</p>
</div>
<div class="col-xs-3 col-sm-3 col-md-3 col-lg-3">
<p>.col-lg-3</p>
</div>
<div class="col-xs-3 col-sm-3 col-md-3 col-lg-3">
<p>.col-lg-3</p>
</div>
</div>
You can also use center-gallery for multiple columns of the same size. Example:
<div class="center-gallery-xs-3">
<div class="col-xs-3 col-sm-3 col-md-3 col-lg-3">
<p>.col-lg-3</p>
</div>
<div class="col-xs-3 col-sm-3 col-md-3 col-lg-3">
<p>.col-lg-3</p>
</div>
<div class="col-xs-3 col-sm-3 col-md-3 col-lg-3">
<p>.col-lg-3</p>
</div>
</div>
To see more usages, check the demonstration on codepen